Hi Carlos,
As Canuck223 mentions, it is primarily the slide in my opinion that makes the difference, it's lighter. It's noticeable when you rack the gun. Don't get me wrong, the K100 is also fantastic! However the factory took the X-Calibur to a different level on the trigger and slide action. The trigger on the X-Cal is smooth throughout the action on DA. Single action is so nice because the reset keeps the trigger back so there is not slack when you come back for the follow up shot. Trigger reset on the K100 is similar but it cannot be as smooth because there is a firing pin block and this 'click' is felt on the trigger when using the K100.
With the X-Cal there is no firing pin block safety so the trigger pulls through clean and slick.
I would never hesitate to buy the K100 as a production/carry gun. You can be competitive on the weekend and carry it if you wish. If you are purely interested in a competition gun, then I would look at the X-Calibur. What I like about this platform is you can have that same frame in a number of configurations - P1 / K100 / X-Cal.
This is nice because you can pick up the gun you need for the application and the ergonomics are the same, apart from slide length. I have those 3 and I appreciate them equally.
I recently stripped out my gun using some instructions from Canuck223 and when I took it to a local gunsmith and showed him the gun he was impressed with the design choices GrandPower made. It's fairly obvious they engineered stuff to last with minimal parts to do the job. It's an elegant design with function, I say it's utilitarian.
With regard to the SP-01 - if you compare it to the K100 or the X-Calibur out of the box with no work done (As it should be for Production) then both the GrandPowers are better in my opinion. The best CZ SP-01 trigger I felt was heavily worked and still the 'slack' on single action is there.